Galvanic cell

ABSTRACT

A galvanic cell is disclosed comprising spaced cathodic and anodic electrodes and an electrolyte having an organic aprotic solvent and a soluble solute such as a Lewis acid. At least one of the electrodes has a conductive support member comprising a metal selected from the group consisting of aluminum, magnesium and beryllium.

United States Patent- [151 3,660,162 Eisenber 51 Ma 2 1972 [541 GALVANICCELL 7 2,739,997 3/1956 Carrick et a]. 1 36/57 3,093,514 6/1963 McCallumet a]. ,136/100 [72] lnlenm" m 3,279,952 10/1966 Minnick 136/100 [73]Assignee: Electrochemica Corporation, Menlo Park, 3,380,855 4/1968 Mahyet al. 1 36/ 100 Calif- 3,508,967 4/1970 Lyall et al. ..l36/20 22 Pl d:Mar. 27 1970 l 1 e Primary Examiner-Anthony Skapars PP- N05Attorney-Robert B. Kennedy 52 us. c1. ..136/83 R, 136/100R [571 ABSTRACT[51] ..l-l0lrnl7/00, A a! n l d d m g vamc ce 1s 1sc ose compnsmg spaceca 0 1c an of Search ..136/l00, 83, anodic electrodes and an electrolytehaving an organic aprolic 136/57 20 solvent and a soluble solute such asa Lewis acid. At least one of the electrodes has a conductive supportmember compris- [56] Rekrmccs Clad ing a metal selected from the groupconsisting of aluminum,

UNITED STATES PATENTS magnesium and beryllium. I

25 Claims, No Drawings 3,468,716 9/1969 Eisenberg "136/100 GALVANIC CELLBACKGROUND OF THE INVENTION This invention relates generally to galvaniccells, and particularly to materials and combinations thereof used ingalvanic cells of the type which employ organic electrolytes.

As is well-known in the battery art, the active electrode materialswhich undergo electrochemical reactions during battery operation mustnormally be mechanically supported by a structure composed of relativelyinactive materials. These electrode support members, or grids as theyare frequently termed, vary widely in shape and configuration. Forexample, they may be simply a piece of screen of a suitable mesh size, apiece of expanded metal, or a plate cast with pockets, holes orindentations.

In addition to providing mechanical support theelectrode support membersalso provide electronic conduction between the active electrodematerials of each cell and externally accessible tenninals to whichanvextemal circuit may be connected. This electronic conductance isrequired for the supply and removal of electrons from the electrodeswhen half-cell electrochemical reactions occur at each electrode duringbattery operation. Thus, the electrode support members normally comprisemetals or metal alloys. But, as indicated above, the support memberitself must not participate appreciably in the electrochemical half-cellreaction, nor must it corrode nor react with and thereby contaminate thecell electrolyte. In other words, the electrode supports must remainessentially passive.

Heretofore, the electrode support members in conventional batteries havealmost invariably been composed of lead alloys, silver, silver platedcopper, nickel or nickel plated steel insomuch as only these have beenfound to meet the aboverecited mechanical and electrochemicalrequirements on a practical, commercial basis. Though these materials doprovide operative electrode support members they simultaneously exhibitseveral undesirable traits, the foremost of which I being their weight.The generally acid or strongly alkaline nature of conventional aqueouselectrolytes has precluded the use of other lighter metals as electrodesupport materials.

Accordingly, it is an object of the present invention to provide animproved galvanic cell.

More particularly, it is an object of the present invention to provide arelatively light weight galvanic cell.

Another object of the invention is to provide a galvanic cell havingelectrode support members which provide sound mechanical support andelectronic conduction, exhibit a relatively low rate of reaction withelectrolytes of the organic type, and yet which are lightweight,malleable, rollable and relatively inexpensive.

SUMMARY OF THE INVENTION Briefly described, the present invention isagalvanic cell comprising spaced cathodic and anodic electrodes and anelectrolyte having an organic aprotic solvent and a soluble solute toprovide electrolytic conduction between said spaced electrodes. At leastone of said electrodes has a conductive support member which comprises ametal selected from the group consisting of aluminum, magnesium andberyllium.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In aqueous electrolytebatteries, that is those in which water is the solvent, appreciableelectrode reaction rate capabilities steel, silver plated copper andeven pure silver are so used. However, according to the principles ofthe present invention a relatively lightweight galvanic cell isconstructed by using aluminum, magnesium or beryllium, either in theirrelatively pure metallic form, in combinations with each other, or asalloys, as electrode supports, and an electrolyte comprising organicaprotic solvents. Such cells have been found to perform well where suchsupport materials support lithium and calcium anodes as well as cathodescomprising metal chlorides, sulfides, fluorides and bromides. Examplesof such anodes are those in which the active material comprises calcium,strontium and barium and the alkali metals of group Ia of the periodicsystem of elements. Examples of such cathodes are those in which theactive material comprises copper chloride, copper bromide, copperfluoride, copper sulfide, silver fluoride, silver difluoride, silverchloride, silver bromide and the halide compounds of nickel, cobalt andmanganese.

The organic aprotic electrolytes comprise a solute which may be a Lewisacid, preferably with a coordinating salt, or any other kind of a saltsufficiently soluble in the organic aprotic solvent to yield anelectrolyte with a specific conductivity of at least 5 X 10 mhos/cm andyet not participate appreciably in the electrode reactions of the cell.Examples of Lewis acids are aluminum fluoride, aluminum chloride,aluminum bromide, boron halides such as boron chloride, boron fluorideand boron bromide antimony fluorides and antimony chlorides. Examples ofsuch other kinds of salts are lithium perchlorate, sodium perchlorateand magnesium perchlorate.

The Lewis acids, or salts are dissolved in aprotic solvents. The Lewisacids may be dissolved either with or without alkali metal halide orearth alkali coordinating compounds such as lithium fluoride, lithiumchloride, lithium bromide, sodium chloride or sodium fluoride. Examplesof the aprotic solvents successfully used include pentacyclic esters,aliphatic ethers, cyclic ethers, nitroparafiins, cyclic ketones,aliphatic nitriles, chlorinated esters, cyclic and aliphatic amines andamides. Where desired, compatible combinations of the just listedaprotic solvents may be used such as those described in U. S. Pat. No.3,468,716. Thus, the particular solvent and solute is largely a matterof choice so long as their combination produces an electrolyte that isaprotic in nature and has sufficient specific conductivity.

The just disclosed electrode support members are not, of course,completely free from corrosive attack by some organic electrolytes.Those combinations of support materials and electrolytes in whichcorrosion occurs more rapidly have nevertheless been found quitesuitable for use in reserve type batteries, that is primary batteries inwhich the electrolyte is introduced just prior to battery operationwhich operative period does not ordinarily exceed 1 week. A 20 X 20 mesh(0.0l0-inch thick wire) aluminum screen type 1 in an aluminum chloridesolution in nitromethane-propylene carbonate solvent mixtures willcorrode at a rate rendering its use limited to such a reserve typebattery where there is an insufficient amount of coordinating salts,such as lithium chloride, in the electrolyte. In general the closer theproportionality between the Lewis acid and coordinating salt to a ratioof 1:1 by weight, the lesser the rate of support corrosion. Thus, onepart by weight of aluminum chloride, a Lewis acid, to one part by weightof lithium chloride, a coordinating salt, provides for minimalcorrosion. For more acidic electrolytes, that is those containing arelatively low proportion of coordinating salt, the life of the supportcan be substantially extended, where desired, by electroplating it withnickel. The proportion of Lewis acid to coordinating salt by weightshould be 1:1.5 and 4.1.

The following three specific examples of material combinations andcompositions have been found to produce galvanic cells having a highlysatisfactory life period for many practical applications:

A 20 X 20 mesh aluminum screen alloy, No. 1100, which is commerciallypure aluminum with a minimum content of 99 percent aluminum, to which analuminum contact tab has been welded on, is used to make a lithium anodeby pressing on in an inert atmosphere of argon, a piece of lithiummetal. A similar piece of aluminum screen is used as a support grid forthe cathode in which a mixture of copper chloride with small additionsof graphite as a conducting additive and a suitable binder is pressed toyield a cathode. Using six such cathodes and seven anodes interleavedwith a nonwoven polypropylene separator a cell is assembled with anelectrolyte comprising by volume 80 percent nitromethane, 20 percentpropylene carbonate containing 3 moles/liter of aluminum chloride and0.3 moles/liter of lithium chloride. The open circuit voltage of thiscell, the construction of which is described more fully in U. S. Pat.No. 3,468,716,'was found to be 3.10 volts at an ambient temperature of20 C. Two cells thus constructed have been discharged at the same timewith two control cells in which the grids were screens of the same mesh,i.e., 20 X '20 mesh, and wire thickness, but made of nickel. As can beseen from Table l, in which the comparison is given, the aluminumequipped cell yields about the same amount of power, but because of alighter weight resultsin a substantial increase of energy density asexpressed in watt-hours per pound.

EXAMPLE ll Two cells are built using aluminum type 1100 grids of thesame mesh as in the preceding example, but electroplated with nickel.These cells are also discharged at 12 amps and in the same electrolyteas Example I, yielding comparable cell voltages and capacities as theother cells. However, due to the lower weight they were capable ofsignificantly larger energy densities as illustrated in the fourthcolumn of Table 1.

EXAMPLE Ill Cells are constructed using perforated sheet of magnesiumalloy type A2318 (96% magnesium, 3% aluminum, 1%zihc), a commercialalloy with a specific gravity of 1.77. Cells are constructed using theseperforated magnesium sheets as supports and filled with the sameelectrolyte as given in Example 1. The energy density yield obtained is15--l8% greater than those of the aluminum cells of Table l TABLEll-ENERGY DENSITY YIELDS OF ORGANIC ELECTROLYTE CELLS WITH NICKEL ANDWITH ALU- MINUBI SUPPORT GRIDS 5 A-H nominal capacity cells dischargedat room temperature at 12 amps Grid type Aluminum Aluminum type 1100plated type 1100 with nickel N1ckel (Example I) (Example II) CellWeight, No. lb s. 0. 320-0. 322 0. 240-0. 245 0. 245-0. 260 Ave. cullvoltage (under ad) 2. 172. 20 2.14-2. 18 2.12-2.17 P orcout lamduiculllcioncy (percent yield of theoretic. capacity) 66-67 6567 68-72 A-lIiluliv. to 1.0 v.

cuto 5. 6-5. 7 5. 5-5. 7 5. 9-6.0 Energy density yield,

Wll/No. ll) 37. 8-39. 2 49-54 50-53. 2

it should, of course, be understood that just-described examples merelyillustrate principles of the invention. The spirit and scope of theinvention isintended to be limited only by the following claims.

1 claim:

1'. A galvanic cell comprising spaced cathodic and anodic electrodes, anelectrolyte having an organic aprotic solvent and soluble solute toprovide electrolytic conduction between conductive support memberconsisting essentially of at least one metal selected from the groupconsisting of aluminum, magnesium, beryllium and alloys thereof. 7

2. A galvanic cell in accordance with claim 1 wherein said conductivesupport member consists essentially of aluminum.

3. A galvanic cell in accordance with claim 1 wherein said conductivesupport member consists essentially of magnesiurn.

4. A galvanic cell in accordance with claim 1 wherein said conductivesupport member consists essentially of aluminum and magnesium.

5. A galvanic cell in accordance with claim 1 wherein said conductivesupport member consists essentially of an aluminum alloy comprising atleast 20 percent aluminum by weight.

6. A galvanic cell in accordance with claim 1 wherein said conductivesupport member consists essentially of a magnesium alloy comprising atleast 20 percent magnesium by weight.

7. A galvanic cell in accordance with claim 1 wherein said one electrodehas an anodic active material supported by said support member, saidanodic active material comprising a metal selected from the groupconsisting of lithium and calcium.

8. A galvanic cell in accordance with claim 1 wherein said one electrodehas a cathodicactive material supported by said support member.

9. A galvanic cell in accordance with claim 8 wherein said activematerial is a halideof a metal selected from the group consisting ofiron, cobalt, nickel, copper, silver, cadmium, mercury and manganese.

10. A galvanic cell in accordance with claim 9 wherein said cathodicactive material comprises silver chloride.

11. A galvanic cell in accordance with claim 9 wherein said cathodicactive material comprises copper chloride.

12. A galvanic cell in accordance with claim 8, wherein said cathodicactive material comprises a sulfide of a metal selected from the groupconsisting of iron, cobalt, nickel, copper, silver, cadmium, mercury andmanganese.

13. A galvanic cell in accordance with claim 1 wherein said solublesolute comprises a Lewis acid.

14. A galvanic cell in accordance with claim 13 wherein said solublesolute further comprises an alkali metal coordinating salt.

15. A galvanic cell in accordance with claim 13 wherein said solublesolute further comprises an earth alkali coordinating salt.

16. A galvanic cell in accordance with claim 14 wherein the proportionsby weight of Lewis acid to alkali metal coordinating salt is between121.5 and 4: 1.

17. A galvanic cell in accordance with claim 15 wherein the proportionsby weight of Lewis acid to earth alkali coordinating salt is between 1:1.5 and 4:1.

18. A galvanic cell in accordance with claim 1 wherein said electrolytehas a specific conductivity of at least 5 X 10 mhos/cm.

19. A galvanic cell comprising spaced cathodic and anodic electrodes, anelectrolyte having an organic aprotic solvent and soluble solute toprovide electrolytic conduction between said spaced electrodes, at leastone of said electrodes having a conductive support member consistingessentially of a first metal selected from the group consisting ofaluminum, magnesium and beryllium and a second metal selected from thegroup consisting of nickel, silver and copper, said first metal,

said soluble solute comprises a Lewis acid and an alkali metalcoordinating salt, and wherein the proportions by weight'of Lewis acidto alkali metal coordinating salt is between 1:15 and 4: l.

25. A galvanic cell in accordance with claim 22 wherein said solublesolute comprises a Lewis acid and an earth alkali coordinating salt, andwherein the proportions by weight of Lewis acid to alkali metalcoordinating salt is between 1:1.5 and 4: l.

2. A galvanic cell in accordance with claim 1 wherein said conductivesupport member consists essentially of aluminum.
 3. A galvanic cell inaccordance with claim 1 wherein said conductive support member consistsessentially of magnesium.
 4. A galvanic cell in accordance with claim 1wherein said conductive support member consists essentially of aluminumand magnesium.
 5. A galvanic cell in accordance with claim 1 whereinsaid conductive support member consists essentially of an aluminum alloycomprising at least 20 percent aluminum by weight.
 6. A galvanic cell inaccordance with claim 1 wherein said conductive support member consistsessentially of a magnesium alloy comprising at least 20 percentmagnesium by weight.
 7. A galvanic cell in accordance with claim 1wherein said one electrode has an anodic active material supported bysaid support member, said anodic active material comprising a metalselected from the group consisting of lithium and calcium.
 8. A galvaniccell in accordance with claim 1 wherein said one electrode has acathodic active material supported by said support member.
 9. A galvaniccell in accordance with claim 8 wherein said active material is a halideof a metal selected from the group consisting of iron, cobalt, nickel,copper, silver, cadmium, mercury and manganese.
 10. A galvanic cell inaccordance with claim 9 wherein said cathodic active material comprisessilver chloride.
 11. A galvanic cell in accordance with claim 9 whereinsaid cathodic active material comprises copper chloride.
 12. A galvaniccell in accordance with claim 8, wherein said cathodic active materialcomprises a sulfide of a metal selected from the group consisting ofiron, cobalt, nickel, copper, silver, cadmium, mercury and manganese.13. A galvanic cell in accordance with claim 1 wherein said solublesolute comprises a Lewis acid.
 14. A galvanic cell in accordance withclaim 13 wherein said soluble solute further comprises an alkali metalcoordinating salt.
 15. A galvanic cell in accordance with claim 13wherein said soluble solute further comprises an earth alkalicoordinating salt.
 16. A galvanic cell in accordance with claim 14wherein the proportions by weight of Lewis acid to alkali metalcoordinating salt is between 1:1.5 and 4:1.
 17. A galvanic cell inaccordance with claim 15 wherein the proportions by weight of Lewis acidto earth alkali coordinating salt is between 1:1.5 and 4:1.
 18. Agalvanic cell in accordance with claim 1 wherein said electrolyte has aspecific conductivity of at least 5 X 10 4 mhos/cm.
 19. A galvanic cellcomprising spaced cathodic and anodic electrodes, an electrolyte havingan organic aprotic solvent and soluble solute to provide electrolyticconduction between said spaced electrodes, at least one of saidelectrodes having a conductive support member consisting essentially ofa first metal selected from the group consisting of aluminum, magnesiumand beryllium and a second metal selected from the group consisting ofnickel, silver and copper, said first metal being plated with saidsecond metal.
 20. A galvanic cell in accordance with claim 19 whereinsaid one electrode has an anodic active material supported on saidsupport member, said anodic active material comprising a metal selectedfrom the group consisting of lithium and calcium.
 21. A galvanic cell inaccordance with claim 19 wherein said one electrode has a cathodicactive material supported by said support member.
 22. A galvanic cellcomprising spaced cathodic and anodic electrodes, an electrolyte havingan organic aprotic solvent and soluble solute to provide electrolyticconduction between said spaced electrodes, at least one of saidelectrodes having a conductive support member at least The surface ofwhich support member consisting essentially of metal selected from thegroup consisting of aluminum, magnesium and beryllium.
 23. A galvaniccell in accordance with claim 22 wherein said electrolyte has a specificconductivity of at least 5 X 10 4 mhos/cm.
 24. A galvanic cell inaccordance with claim 22 wherein said soluble solute comprises a Lewisacid and an alkali metal coordinating salt, and wherein the proportionsby weight of Lewis acid to alkali metal coordinating salt is between1:1.5 and 4:1.
 25. A galvanic cell in accordance with claim 22 whereinsaid soluble solute comprises a Lewis acid and an earth alkalicoordinating salt, and wherein the proportions by weight of Lewis acidto alkali metal coordinating salt is between 1:1.5 and 4:1.